This invention relates generally to water-cooled internal combustion engines and in particular to apparatus and methods for repairing water-cooled internal combustion engines.
Water-cooled internal combustion engines typically have one or more cylinder heads that define the upper portions of the combustion chambers of the engine. Each of the cylinder heads will ordinarily have various coolant passages that allow engine coolant (usually a mixture of ethylene glycol or propylene glycol and water) to flow through the cylinder head to cool the cylinder head in the vicinity of the combustion chamber, exhaust valves and other critical areas. Experience has shown, however, that cracks or other damage can occur in the boundary walls separating the coolant passages from other areas of the cylinder head, especially on high-mileage engines or if the engine has experienced overheating due to coolant loss.
It is desirable to repair, rather than replace, damaged cylinder heads because of the high cost associated with replacement of the damaged cylinder head. According to one prior art method, a crack sealant is introduced into the engine coolant and the engine is run up to temperature for a period of time. The heat and pressure of the engine coolant forces the crack sealant into the damaged area to seal the crack. Because this prior art method relies on coolant pressure (typically 7-15 psi) to force coolant containing the crack sealant into the crack, this method is adequate only if the crack leads from a coolant passage to the outside or other region of the cylinder head that is at a lower pressure than the coolant pressure.
In a conventional diesel engine such as the International® VT365 (also known as the 6.0L Ford® Powerstroke™ diesel engine) fuel is supplied to the fuel injectors through a fuel passageway formed in the cylinder head. The fuel in the fuel passageway is supplied from the fuel pump at a medium pressure (about 60 psi) and flows through the fuel passageway into each of the fuel injector bores formed in the cylinder head. The fuel injectors intake the medium pressure fuel from the fuel injector bores and inject the fuel into the combustion chamber at very high pressure (above 3000 psi).
It has been discovered that frequently cracks or other damage may occur in the boundary wall separating the fuel injector bores from the coolant passages. When this occurs, fuel inside the fuel injector bore is forced by the fuel pump through the crack where it enters the coolant passage and mixes with the engine coolant. Prior art methods of injecting crack sealant into the cooling system are inadequate to repair this type of crack because the fuel pressure is greater than the coolant pressure and therefore the crack sealant cannot be forced into the crack to repair it.